<template>
  <div>
    <router-link to="/" tag="div" class="header-abs" v-show="showAbs">
      <div class="iconfont back-icon">&#xe624;</div>
    </router-link>
    <div class="header-fixed" v-show="!showAbs" :style="opacityStyle">
      <div class="header-left">
        <router-link to="/">
          <div class="iconfont back-icon">&#xe624;</div>
        </router-link>
      </div>
      <div class="header-title">景点详情</div>
    </div>
  </div>
</template>

<script>
export default {
  name: 'DetailHeader',
  data () {
    return {
      showAbs: true,
      opacityStyle: {
        opacity: 0
      }
    }
  },
  methods: {
    handleScroll () {
      const top = document.documentElement.scrollTop
      if (top > 60) {
        let opacity = top / 140
        opacity = opacity > 1 ? 1 : opacity
        this.opacityStyle = {opacity}
        this.showAbs = false
      } else {
        this.showAbs = true
      }
    }
  },
  activated () {
    window.addEventListener('scroll', this.handleScroll)
  },
  // 记得对全局事件解绑
  deactivated () {
    window.removeEventListener('scroll', this.handleScroll)
  }
}
</script>

<style lang='stylus' scoped>
  @import "~styles/varibles.styl"
  .header-abs
    position absolute
    left .2rem
    top .2rem
    width .8rem
    height .8rem
    line-height .8rem
    text-align center
    border-radius .4rem
    background rgba(0,0,0, .8)
    .back-icon
      color #fff
      font-size .4rem
  .header-fixed
    z-index 2
    position fixed
    top 0
    left 0
    right 0
    overflow hidden
    line-height $headerHeight
    background-color $bgColor
    color #fff
    .header-left
        width .64rem
        float left
        .back-icon
          text-align center
          font-size .4rem
          color #fff
    .header-title
      flex 1
      overflow hidden
      text-align center
      font-size .32rem
</style>
